It's at least 59 years overdue; coastal towns are warned

New findings have sharply raised the prospect that a major earthquake and tidal wave will hit the Oregon coast within the next 50 years.

As late as this spring, published reports put the likelihood of such an event over 50 years at 10 to 14 percent. Now the probability is calculated to be closer to 70-80 percent, says Chris Goldfinger of Albany, an Oregon State University scientist who has extensively studied the the long history of quakes in Cascadia Subduction Zone.

Goldfinger is the director of the Active Tectonics and Seafloor Mapping Laboratory at OSU. He and others have prepared a scientific paper on their latest findings concerning the frequency of earthquakes along the zone, which underlies western Oregon and surfaces 30-80 miles off the coast.

Their paper has been under review by the U.S. Geological Service for a year, but its findings have begun to be quietly circulated among coastal communities.

In Yachats, for example, James Roddey, the earth sciences information officer for the Oregon Department of Geology and Mineral Studies, spoke to the city council in July. The town's newsletter summarized his warnings under the headline "Natural Disaster Imminent on Oregon Coast."

In an interview with the Democrat-Herald last week, Roddey said the upshot of the new research is that the southern part of the quake fault off the coast has ruptured almost twice as often as the northern portion, on which previous predictions had been based.

In a separate interview, Goldfinger said his research showed quakes roughly every 200 to 300 years, and the last one shook the coast in 1700.

This, he points out, puts us at least 59 years past the average repeat cycle of major quakes along the southern part of the fault.

These are quakes of a size that, according to Roddey, would cause a great deal of destruction as far inland as Corvallis, Albany and Portland.

When will the next one happen?

"Chances are that a lot of people now alive will see it," Goldfinger said.

Roddey said that when he tells audiences about this, the usual first response is "stunned silence, complete total denial."

But not for long. The Yachats newsletter, for example, urged readers to prepare and to attend an upcoming class of a "Citizens Emergency Response Team."

The findings are based on the frequency of underwater landslides caused by quakes over thousands of years. The timing of the ancient slides can be determined by radiocarbon dating.

Goldfinger says the fault line is so close to the coast that tsunami warnings by siren or other means won't do much good when the next big one hits.

"The wave will come in before the siren goes off," he said. "The earthquake is the warning."